The conventional submergible motor pump assembly has been unitarily constructed with a pump section and a motor section, and such a construction could not be thought to be convenient in respect to disassembly and reassembly. On the other hand, a submergible motor pump to be used in particular for civil work or the like has to be adequately maintained because the wear and the damage of the pump elements are more conspicuous due to suction of dirty liquid containing sand, mud and the like. Further, the motor section may likely be subjected to overload because of severe conditions of operation. Accordingly the submergible motor pump assembly in particular for the use in civil work or the like is to be adequately maintained regularly.
Many of the conventional submergible motor pump assemblies are, however, difficult in disassembly and reassembly. Particular difficulty is found in disassembly of the motor section, and there are pump assemblies which cannot be disassembled without disassembling the pump section in advance of the disassembly of the motor section. Further, there are such pump constructions wherein in case of inspection of the mechanical seal the stuffing box oil cannot be drained out unless the impeller is dismantled. In one example of such construction, when only the pump cover at the periphery of the motor which serves to pass the water delivered from the pump section upward is desired to be dismantled, both the motor frame and the rotor have to be dismantled or the upper bracket of the motor has to be dismantled, which means the motor will be substantially entirely disassembled. In another example of such constructions the mounting piece for the cable connector is fixed to the pump cover and when it is desired to disconnect the cable connector, the cable connector cannot be disconnected except from inside of the pump cover and if the pump cover is therefore dismantled, the lead wire from the stator coil connected to the cable has to be drawn out simultaneously.
FIG. 1 is the drawing showing the seal means for the shaft of the pump of prior art adapted to deliver the liquid or slurry containing foreign matter.
The pump shaft 7 integral with the motor shaft extends through the shaft sealing means 6 and also through the oil seal 9 with the collar 20 disposed between the shaft seal means and the oil seal, said oil seal 9 being attached to the intermediate casing 2 connecting the pump casing and the motor frame and forming a part of the pump casing to the end of the shaft is secured the impeller 18 via a key and a nut 17 is provided for fixing the impeller at the end of said shaft. In the conventional sealing means of the kind above explained, a mechanical seal or a gland packing is used at the rear side of the impeller. Without protection, the mechanical seal or gland packing will be exposed to the slurry. Therefore, the oil seal as shown in FIG. 1 or a labyrinth seal or the like not shown is provided below the mechanical seal so as to prevent ingress of the slurry. It has been found, however, that the oil seal or labyrinth seal alone could not completely prevent ingress of the slurry.
FIG. 2 is the vertical sectional view of the cable connector for the submergible motor pump assembly showing a conventional example thereof.
The cable 54 and the core wires 111 are connected together by means of the connecting member 112. The terminal of the cable is formed by the hermetic material 113 with a flange, said hermetic material 113 being molded of rubber integrally with the connecting members 112 together with the cable 54 and the core wires 111 provided at the opposite side of the connecting member. Then the cover 114 is placed over the hermetic material 113 and the screws with sealing means are turned into the motor cover 41 through the holes of the cover 114 and the hermetic material 113, the cover 114 thus being secured to provide sealing effect.
According to the outlet construction for the cable in the conventional submergible motor pump, the hermetic material 113 is formed integrally with the outer cover or the like of the cable 54. Therefore, it has to be manufactured at a certain specialized factory and it may take time to procure an alternate element for replacement thereof. Besides, it is impossible to exchange only the cable 54 in the case of repair and thus such a construction as above will not be suitable for the pumps handling the slurry or the like which must be disassembled or reassembled rather frequently, to say nothing of periodical or optional frequency in case water tightness is impaired.